In the technical field relative to the formation of sashes for doors and windows, the design comprises two essential components: the so-called double glazing unit and the supporting frame for the double glazing unit and the functional accessories relating to the correct assembly and use of the sash formed.
Usually, the double glazing unit comprises:                at least a pair of sheets of glass (with equal or different perimeter dimensions according to the planned use) positioned facing each other and parallel to each other        a spacer and joining element positioned on the four sides formed by the sheets of glass;        a structural component made of synthetic material applied along the outer perimeter defined by the spacer in order to increase the physical characteristics of the double glazing unit formed and also to increase the thermal insulation of the chamber present between the two sheets of glass and the seal to moisture.The frame which mounts the double glazing comprises:        a pair of uprights and crosspieces made of a metallic material associated with the edges of the double glazing unit to form the supporting frame of the double glazing unit;        each of the uprights and the crosspieces has a tubular profile shaped to define accessory zones for application of seals and at least one longitudinal channel for applying functional elements (for example, hinges) or elements for operating/closing the sash such as slidable rods or striker elements.        
This frame interacts with the fixed counterframe applied to the opening of the room in which the sash is mounted. The fixed counterframe has a profile and accessories which share the accessories present on the frame of the sash.
This type of, so-called, traditional sash structure, even though functionally reliable, has limits of an aesthetic, assembly time and costs and thermal sealing type.
For these reasons, attempts have been made, over time, to modify the basic structures to obtain better results in terms of appearance, rationalisation of frame components and thermal sealing characteristics.
Examples of prior art solutions which are able to modify the structure of the sash frame are known from patent documents EP2315900 and EP2722473 (in the name of the same Applicant as this invention) wherein the frame is without uprights and crosspieces and the perimeter edges of the sheets of glass (forming a cavity) are used to house only the tubular parts of the metal profile useful for applying the supporting and operating accessories and the sash closing/opening accessories associated with the sheets of glass.
Another prior art solution is described in patent document FR 2572766 wherein the frame consists of a hybrid rubber-metal structure.
In other words, a rubber block is housed inside the cavity of the double glazing unit (associated on both sides only to the inner part of the sheets of glass) equipped with a shaped seat which houses, at least partially, in slidable coupling mode (before assembly on the double glazing unit) a complete metal profile configured to define both the seats for housing the control and operating accessories and the lateral actuation accessories such as a handle which are connected by subsequent machining on one of the sheets of glass and on the rubber.
Another solution is known in the prior art from patent document EP 937.856 wherein a frame structure is associated with an inner surface of one of the sheets of glass. The frame comprises a first lower half-chamber supporting the operating components and a second tubular chamber designed to guarantee the passage of the screws for fixing the operating components.
The frame is located asymmetrically and rests fully on the largest sheet of glass with the relative adhesive glue, whilst the other side, the difference in distance is compensated by a greater use of structural component and/or glue.
This embodiment of a sash has the drawback of reduced structural sealing; the frame is asymmetrical and has two different tubularities so it does not represent a structural component with mechanical sealing for the pair of sheets of glass and can be used only on pairs of sheets of glass of different dimensions, that is, with reduced adaptation to frames of different dimensions and types of opening.
Another prior art solution is described in patent document DE 298 12 574 U1. In this solution there are two different profiles, one for each inner side of the glass, each glued to the surface of the glass. The upper portion of the two profiles protrudes towards the centre of the compartment where there is a thermal break seal in contact on both sides with the two portions of the profile. Moreover, the two profiles form an outer supporting surface for the hardware and a half-tubularity designed to allow the passage of fixing screws of the central hardware which are able to reach the central seal thanks to its suitable shaping in the central portion.
This solution, like the previous one, is also a solution with a frame of reduced structural seal; the frame is, in effect, in two parts which are separate and in direct contact with the corresponding sheets of glass. The structure of this frame can only be used on pairs of sheets of glass with different dimensions, that is, with reduced adaptation to frames of different dimensions and opening types.
All these solutions, although they are a considerable improvement with respect to the structure of the traditional sash, have still not eliminated some and further drawbacks, such as weight of the sash, reduction in component and assembly costs and, also, the possibility of adapting the sash to fixed counterframes which are already mounted.
There is currently a greatly felt need for the adaptability of the sash also to counterframes already present since it would drastically reduce the replacement costs without involving invasive and awkward works in closed environments.